The number 81980
81980 is a composite number with 12 divisors. Its prime factorisation is × 5 × 4099. Divisors (12): 1, 2, 4, 5, 10, 20, 4099, 8198, 16396, 20495, 40990, 81980.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
81980 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
81980 is composite. Its prime factorisation is
- 3
The divisors add up to 172200; without 81980 itself that is 90220, so 81980 is abundant (90220 is more than 81980). Euler's totient φ(81980) = 32784 numbers up to 81980 share no factor with it.
- 4
The digits of 81980 add up to 26, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 45 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81980 = 2^{2} \times 5 \times 4099 \]81980 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 172200 |
| Euler totient φ(n) | 32784 |
| Square | 6720720400 |
| Cube | 550964658392000 |
| Square root | 286.321498 (= 2√20495) |
| Digit sum / digital root | 26 / 8 |
| Collatz steps to 1 | 45 |
| Scientific notation | 8.198 × |
81980 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand nine hundred and eighty |
| Binary (base 2) | 10100000000111100 |
| Octal (base 8) | 240074 |
| Hexadecimal (base 16) | 1403C |
| Base 3 | 11011110022 |
| As time | 81980 seconds = 22 h 46 min 20 s |
Is 81980 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (81980 ÷ 2 = 40990) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | No (remainder 2) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (81980 ÷ 4 = 20495) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (81980 ÷ 5 = 16396) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 2) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 3) | A number is divisible by 7 if double the last digit and subtract it from the rest: the result is a multiple of 7. |
| 8 | No (remainder 4) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 8) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (81980 ÷ 10 = 8198) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 8) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 81980 a prime number?
No. 81980 = × 5 × 4099, so it is divisible by 2.
What are the factors of 81980?
1, 2, 4, 5, 10, 20, 4099, 8198, 16396, 20495, 40990, 81980.
What is 81980 in binary?
10100000000111100 (hexadecimal 1403C, octal 240074).
What is the square root of 81980?
About 286.3215, exactly 2√20495.
Is 81980 divisible by 3?
No. Its digits add up to 26, which is not a multiple of 3.
What is special about the number 81980?
It is a composite number with 12 divisors.